Unsurprisingly, that's one of the key assets of Damn Small Linux, and version 4.4.10 continues the tradition. It weighs in at a 50MB ISO file that can be written directly to a disc or flash drive.
Read it here
As part of a survival toolkit, Damn Small Linux could be something of a saviour. Earlier this year, this writer used a previous release of the distribution to excise a couple of gigabytes of files from an otherwise-locked-down Vista installation, and while it didn't save the machine concerned from complete reinstall, it did rescue an awful lot of data. It did it with no fuss, utter simplicity and earned a lot of appreciation as a result.